This invention relates to a dryness sensor device and method for a clothes dryer.
Electronic control systems are commonly used on appliances, including clothes washers and dryers to control the operation of the appliance.
Prior art clothes dryers were controlled by a control system which limited the run time of the dryer based solely on time. The dryer would run for a set amount of time, regardless if the clothes inside were dry or not. Today's more energy conscious consumers create a need for more efficient operation of appliances. Therefore, it is desirable to have an appliance such as a clothes dryer appliance which would turn itself off once the items are completely dried.
Dryers having dryness sensors are known. For example, published U.S. Patent Application Publication No. U.S. 2004/0036486 discloses a dryness measurement device for sensing a dryness status of laundry. That invention uses an electrode sensor for sensing the dryness status of the laundry and measuring the current dryness status by a variance of voltage which is charged in a capacitor based on a variance of resistance of the electrode sensor. In other words, to sense dryness, this invention measures the voltage which is charged on a capacitor.
Another example of a drying appliance which uses a sensor for sensing dryness of the articles being dried is shown in U.S. Pat. No. 4,215,486. This patent discloses a storage capacitor charged from a DC voltage source together with the laundry resistance resulting from wet laundry bridging two electrodes and resistance is determined. In order for the system to work, a capacitor must be charged. Thus, it is desirable to have a dryness sensing device which does not rely on the charge stored in a capacitor.
The primary objective of the present invention is to provide an improved dryness sensor device and method for a clothes dryer.
A further objective of the present invention is to provide a drying appliance which effectively senses the dryness of the articles being dried.
A further objective of the present invention is the provision of a drying appliance in which the dryness sensor saves energy by shutting down the appliance when the clothes have reached proper dryness.
A further objective of the present invention is to provide a method for drying articles which stops the drying process when the articles reach the proper dryness level.
A further objective of the present invention is a provision of a dryness sensor which is economical to manufacture, durable in use, and efficient in operation.
These and other objects of the invention will be apparent from the specification and claims that follow.
A feature of the present invention involves a dryness sensing device in a drying appliance which uses an integrated circuit which is configured as an application specific integrated circuit.
A further feature of the present invention involves a dryness sensing device in a drying appliance wherein a current source is integrated into an application specific integrated circuit.
A further feature of the present invention involves a dryness sensing device in a drying appliance wherein a current source is configured as a current mirror.
A further feature of the present invention involves a dryness sensing device in a drying appliance wherein a current source is driven by a programmable current source.
A further feature of the present invention involves a dryness sensing device in a drying appliance wherein an op amp and a voltage divider circuit produces voltage input to an analog digital converter from a point electrically between an electrical current source and an electrical ground.
A further feature of the present invention involves a dryness sensing device in a drying appliance configured with at least one electrical resistor in series with a current source and sensor bars.
A further feature of the present invention involves a dryness sensing device wherein at least one sensor bar is electrically connected to an application specific integrated circuit.
A further feature of the present invention involves a method for sensing dryness comprising the step of converting an analog voltage reading which is across at least two sensor bars into a digital signal for input into a microprocessor.
A further feature of the present invention involves a method for sensing dryness comprising the step of using an application specific integrated circuit for calculating the electrical resistance of an article being dried.